Power plants for military land vehicles of the wheeled or tracked type usually comprise a piston engine and variable speed ratio transmission arranged in abutting in-line relation. Often the transmission includes a flanged housing having a ring of bolt holes designed to individually fit on threaded studs premounted in a face of the engine block; nuts are threaded onto the exposed portions of the studs to rigidly fasten the transmission housing to the engine.
It is necessary that during the act of bolting the transmission onto the engine the drive components within the transmission housing automatically mate with companion drive components in the engine. Often the engine drive component is an internally splined collar carried by the engine flywheel; the mating component in the transmission housing is in that case an externally splined shaft. There is an installation problem due to the fact that the splines on one component can be circumferentially misaligned from the grooves on the other component; the transmission housing often obscures the drive components so that manual rotation of one drive component into precise circumferential alignment with the other drive component becomes a difficult or uncertain trial-and-error process.
Another problem concerns operation of military vehicles in arctic climates. At initial engine start-up some of the drive components in the transmission, such as the transmission input shaft, input gearing and torque converter components, are operatively connected to the flywheel for conjoint rotation therewith. At sub-zero temperatures the lubricant for the various drive components in the transmission is in a relatively cold viscous state so that some starter effort is required to rotate the transmission components; this somewhat lowers the engine cranking speed, and makes it more difficult to start the engine.
Some military vehicles have a manual-disconnect system between the engine flywheel and the input drive component in the transmission to minimize cold weather starting problems. The present invention is concerned with such a disconnect system. Principal objects of the invention are to provide a disconnect system that can be retained in a retracted disconnect mode while the transmission is being bolted to the engine, either at initial assembly or after a repair operation on either the engine or transmission. Another object is to provide an engine-transmission disconnect system that can be set to automatically connect the engine flywheel to the transmission input drive component subsequent to the process of bolting the transmission onto the engine. A further object is to provide an engine-transmission disconnect system that is relatively strong, simple and compact, while not requiring the technician to precisely line up splined areas on the engine and transmission drive components during an engine-transmission assembly operation.